netdev - Re: [PATCH] stmmac: CSR clock configuration fix

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Date:   Thu, 22 Dec 2016 10:15:20 +0000
From:   Joao Pinto <Joao.Pinto@...opsys.com>
To:     David Miller <davem@...emloft.net>, <Joao.Pinto@...opsys.com>
CC:     <peppe.cavallaro@...com>, <hock.leong.kweh@...el.com>,
        <niklas.cassel@...s.com>, <pavel@....cz>,
        <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>
Subject: Re: [PATCH] stmmac: CSR clock configuration fix

Às 6:21 PM de 12/21/2016, David Miller escreveu:
> From: Joao Pinto <Joao.Pinto@...opsys.com>
> Date: Tue, 20 Dec 2016 11:21:47 +0000
> 
>> When testing stmmac with my QoS reference design I checked a problem in the
>> CSR clock configuration that was impossibilitating the phy discovery, since
>> every read operation returned 0x0000ffff. This patch fixes the issue.
>>
>> Signed-off-by: Joao Pinto <jpinto@...opsys.com>
> 
> This isn't enough.
> 
> It looks like various parts of this driver set the mask field
> differently.
> 
> dwmac1000_core.c and dwmac100_core.c set the mask to be the low bits.
> 
> But dwmac4_core.c uses GENMASK(11, 8) which means the mask is a value
> which is shifted up already.
> 
> So your patch will break chips driven by dwmac4_core.c.

I am using a GMAC4 reference design to test the patches. The clock configuration
as is, does not work, resulting in the phy discovery failure. By applying this
patch I am able to set the clock value properly.

I am going to check in the Databook of GMAC4 and older versions in order to
justify better.

> 
> In order for your change to be correct you must consolidate all of
> these various pieces to use the same convention.
> 

Thanks.